Telephone-exchange system.



L. H. JOHNSON.

TELEPHONE EXCHANGE SYSTEM.

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"UNT BTB PTEN FFT@@ LEWIS H. JOHNSON, OF BLOOMFIELD, NEVJ JERSEY,ASSIGNOR T WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEVI YORK, N. Y.,A CORPORATION OF NEVJ' YORK.

TELEPHONE-EXCHANGE SYSTEM.

Specification of Letters Patent.

Patented J an. 16, 1917.

Application filed May 26, 1916. Serial No. 99,976.

To all whom it may concern:

Be it known that I, Lnwis H. J OHNSON, a citizen of the United States,residing at Bloomfield, in the county of Essex and State of New Jersey,have invented certain new and useful Improvements in Telephone- ExchangeSystems, of which the following is a full, clear, concise, and exactdescription.

This invention relates to telephone exchange systems, and moreparticularly to such systems of the central energy type in which anoperators telephone set is automatically connected to and disconnectedfrom a calling telephone line.

The object of this invention is the provision of means for increasingthe efliciency of the operators of a telephone exchange and forfacilitating the completing of connections between subscribers.

In accordance with this invention, a tele phone exchange system, inwhich the operators telephone set is automatically connected to acalling telephone line upon the connection of a link circuit therewith,is provided with circuits and apparatus, and is so organized that whilethe operators telephone set is connected to one calling telephone line,it cannot be connected to any other calling line, but a secondconnection may be prepared during the existence of the first, so thatupon the disconnection of the operators telephone set from the firstcalling line, it will be immediately connected to the calling lineforming a part of the prepared connection. This invention is animprovement on that disclosed in the application of Henry P. Clausen,Ser. No. 59,972, filed November 6, 1915, in that less apparatus isrequired for accomplishing the desired result.

More specifically, this invention contemplates a telephone exchangesystem in which there are link circuits for interconnecting the lines,and a relay associated with each link circuit for automaticallyconnecting the operators telephone set with the talking strands thereofwhen connected with a calling telephone line. A common relay associatedwith all link circuits at the same position operates upon the operationof any listening relay to alter the resistance of the circuits of allother listening relays to prevent the operation of any one of them whenthe corresponding link circuit is connected with another calling line,whereby an operator is prevented from being connected to more than oneline at the same time.

This invention is illustrated in the accompanying drawing in which thereare shown ordinary subscribers lines A, B, C and D (subscribers lines B,C, and D being indicated merely by the answering jacks thereof) and twocord circuits E and F for interconnecting the subscribers lines. Theapparatus in each cord circuit -is exactly alike, and the same referencecharacters will be used in each to indicate the same apparatus.

Assuming that subscriber A wishes to converse with subscriber B, A willsignal the central office in the usual manner, whereupon the operatorwill insert the answering plug of the cord circuit E into the jackassociated with As line, causing the operation of sleeve relay andsupervisory relay 6. The operation of supervisory relay 6 causes theoperation of listening relay 7 over a circuit from battery through theright-hand winding of common relay 8, contact 14 thereof, commonconductor 9, normal contact of relay 10, both windings of relay 7,alternate contact of supervisory relay 6 and supervisory lamp 11 toground. The operation of the listening relay 7 connects an operatorstelephone set 12 to the talking strands of the cord circuit E, and, bythe engagement of the lower armature with contact 13, short-circuits thelower winding thereof. Upon the shortcircuiting of the lower winding ofrelay 7, relay 8 operates, opening its contact 14, thereby removing theshort circuit of the left-hand winding of this relay which is nowincluded in the circuit with the right-hand winding of relay 8 and theupper winding of listening relay 7. The left-hand winding of relay 8 isof highresistance so that no'other listening relay in that position willwhen its circuit is completed, receive sufiicient current to permit theoperation thereof. After ascertaining that subscriber A wishes to beconnected to the line of subscriber B, the operator inserts the callingplug into the jack of Bs line, causing the operation of relay 10, whichopens the normal contact thereof, permitting the listening relay 7 ofthe cord circuit E and the common relay 8 to release. Relay 8,inreleasing, short-circuits its lefthand winding. The operation of relayalso closes the right-hand contact thereof, causing the supervisory lamp21 to light. The operator now actuates ringing key 22 to send ringingcurrent out over Bs line to operate the call bell thereat. Subscriber B,in responding, removes the receiver from the switch-hook, causing theoperation of supervisory relay 28 to eiface supervisory signal 21. Uponthe completion of the conversation, subscribers A and B restore thereceivers to the switchhooks, causing the supervisory lamps 11 and 21 tolight to furnish disconnect signals. The operator then withdraws theplugs from the jacks, whereupon all apparatus returns to normal.

Supposing that while the operator was busy completing connection betweensubscribers A and B, but before the calling plug of cord circuit E wasinserted into the ack of Bs line, subscriber C had initiated a call. Theoperator could take up this call by inserting the answering plug of cordcircuit F into the jack of Us line, thereby operating relays 5 and 6 ofthis cord circuit. While the circuit of listening relay 7 of cordcircuit F is completed by the operation of supervisory relay 6 thereof,listening relay 7 will not operate, for both windings of the commonrelay 8 are in circuit with the two windings of the listening relay.Relay 7, however, will operate as soon as the operator has inserted thecalling plug of cord circuit E into the jack of Bs line, for theoperation of relay 10 of cord circuit E opens the circuit of andreleases relay 8, thereupon establishing the short-circuit for theleft-hand high resistance winding, permitting listening relay 7 of cordcircuit F to operate to connect the operators telephone circuit to thetalking strands of cord circuit F. The operation of the listening relayof this cord circuit also short-circuits its lower winding, permittingcommon relay 8 to again operate to remove the short circuit of itshigh-re sistance winding and include it in the circuit with bothwindings of all of the listening relays in the position.

What is claimed is:

1. In a telephone exchange system, subscribers lines terminating at acentral oflice, link circuits for interconnecting the lines, anoperators telephone set, a relay having an operating winding associatedwith each link circuit operating upon connection thereof with a callingline to include the operators telephone set in circuit therewith, acircuit multipled to and normally including the operating winding ofeach relay, and means in said circuit operating upon the operation ofany one of said relays to increase the resistance of said circuit toprevent the operation of the relay of another link circuit whenconnected with another line.

2. In a telephone exchange system, subscribers lines terminating at acentral ofiice, link circuits for interconnecting the lines, anoperators telephone set, a relay having an operating winding associatedwith each link circuit operating upon connection thereof with a callingline to include the operators telephone set in circuit therewith, anoperating circuit, a branch from said operating circuit for each relayand normally including the operating winding thereof, and means in saidcircuit operating upon the operation of any one of said relays to alterthe resistance of said circuit to prevent the operation of the relay ofanother link circuit when connected with another line.

3. In a telephone exchange system, subscribers lines terminating at acentral office, link circuits for interconnecting the lines, anoperators telephone set, a relay having an operating winding associatedwith each link circuit operating upon connection thereof with a callingline to include the operators telephone set in circuit therewith, acircuit multipled to and normally including the operating winding ofeach relay, and a common relay in said circuit operating upon theoperation of any one of said individual relays to alter the resistanceof said circuit to prevent the operation of the relay individual toanother link circuit when connected with another line.

4:. In a telephone exchange system, subscribers lines terminating at acentral ofiice, link circuits for interconnecting the lines, anoperators telephone set, a relay having an operating winding associatedwith each link circuit operating upon connection thereof with a callingline to include the operators telephone set in circuit therewith, acircuit multipled to the operating winding of each relay, and a doublewound common relay having one winding normally short-circuited in saidcircuit operating upon the operation of any one of said individualrelays to remove the short circuit and include both windings in saidcircuit to prevent the operation of the relay individual to another linkcircuit when connected with another line.

In witness whereof, I hereunto subscribe my name this 24th day of May A.D., 1916.

LEWIS H. JOHNSON.

Copies of this patent may be obtained for five cents each, by addressingthe Commissioner of Iatents. Washington, D. G.

